The Department of Immunology seeks funding to provide a substantial upgrade of its Cell Analysis Facility. The Cell Analysis Facility was established in 1991 as a core resource offering a range of services and expertise to investigators in the University of Washington and local research community. Providing state-of-the-art analytical instrumentation requires that a range of services be offered. These include consulting on experimental design, execution of experiments (modifying existing instrumentation where necessary), archiving and distribution of data files, interpretation of experimental results and the production of effective graphics for publication and presentation. Instrumentation includes benchtop analyzes, a dual laser cell sorter, and a scanning confocal microscope. During 1997, the Facility was used by more than 50 investigators in the University of Washington as well as several investigators from other institutions. The cell sorter was used by 58% of billable hours by 37 investigators. from 17 different departments on campus and supported by 60 different sources of funding. The current cell sorter, a nine-year-old dual argon laser FACStarPlus, is no longer state of the art and is not able to perform the analyses needed by the larger group of NIH-funded researchers the Facility serves. The instrument is capable of 4-color analysis (in some cases), cannot analyses newer red-excited fluorescent dyes, is limited to sorting at about 3,000 cells per second, and is operated by an outdated acquisition computer software that is no longer supported by the manufacturer. Although an upgrade of the existing instrument was considered, the increased number of component failures as well as the aged design of several subsystems argues for replacement with a contemporary instrument. Several projects cannot be performed because they require the ability to sort large numbers of cells for subsequent analysis. Others need to sort relatively rare cells that do not service extended periods outside of popular culture conditions. And other have had problems with instrument access when needed. Current research objectives requires an instrument capable of analyzing 4 o 6-color fluorescence, exciting red-excited fluorochromes, sorting at high speeds (above 20,000 events per second), sorting single cells into microtitre dishes, as well as the ability to examine cellular physiology in flow. The instrumentation requested will provide for current and future user needs.